The present invention relates generally to spacecraft and control methods therefor, and more particularly, to an equatorial-normal body-stabilized spacecraft that operates in an inclined orbit and a method of controlling the spacecraft.
The assignee of the present invention manufactures and deploys communication satellites or spacecraft that orbit the Earth. Heretofore, certain spacecraft have been launched and positioned in geosynchronous equatorial or non-inclined orbits. In such geosynchronous equatorial or non-inclined orbits, the spacecraft is controlled to point its payload (communication antennas or instruments) at the Earth and point its solar arrays at the sun. When the spacecraft is positioned in a geosynchronous equatorial or non-inclined orbit, it is controlled to maintain sun pointing by rotating the body of the spacecraft around a single axis, which is the pitch axis. The pitch axis is normal to the orbit plane.
However, for conventional spacecraft positioned in inclined orbits, control is achieved by rotating or steering the spacecraft about two axes, the pitch and yaw axes, to maintain Earth and sun pointing. This is referred to as yaw steering.
It is an objective of the present invention to provide for an equatorial-normal body-stabilized spacecraft that operates in an inclined orbit. It is another objective of the present invention to provide for an equatorial-normal body-stabilized spacecraft that operates in an inclined orbit that is controlled to provide Earth-pointing payloads and sun-pointing solar arrays wherein the spacecraft body and solar arrays each rotate only around a single axis. It is another objective of the present invention to provide for an improved method of controlling a spacecraft to provide payload pointing with minimal spacecraft rotation, in that all large-angle spacecraft rotation occurs around the pitch axis.